The present invention relates to a method for the preparation of a polyurea resin. More particularly, the invention relates to a method for the preparation of a polyurea resin having a high hardness and usefulness as a molding material of various kinds of rollers, e.g., calendering rollers, used in the industries of paper, fabrics, magnetic tapes and the like, casters and the like as well as excellent heat resistance by the reaction of a polyamine compound and a polyisocyanate compound.
As is disclosed in Japanese Patent Kokai 63-202612, a method is known for the preparation of a high-hardness polyurea resin having usefulness as a material of high-hardness rollers and the like, in which an aromatic polyamine compound such as a derivative of aminobenzoic acid and a polyisocyanate are reacted. This method, however, is not quite satisfactory because the hardness of the polyurea resin prepared by this method is not high enough for the purpose although the resin obtained by the method is excellent in respect of the impact strength and heat resistance.
Alternatively, a proposal is made in Japanese Patent Kokai 64-1715, according to which a polyurea resin is prepared by the reaction of an aromatic polyamine compound and a cyclic trimer of an aliphatic polyisocyanate compound. Although the resin obtained by this method has a sufficiently high hardness, the resin cannot be used in practical applications where high toughness of the resin is required because of the very poor impact strength of the resin.
Thus, no prior art method has been established by which a polyurea resin having a high hardness and excellent heat resistance and still having good impact strength suitable for practical applications can be easily prepared.